1. Field of the Invention
The present invention relates to a method and a related apparatus for diagnosing an optical disk drive. In particular, the present invention discloses a method and a related apparatus for diagnosing crosstalk within an optical pick-up unit by utilizing firmware of the optical disk drive.
2. Description of the Prior Art
Please refer to FIG. 1, which is a block diagram of a prior art optical disk drive 10. The optical disk drive 10 is used for reading data stored on an optical disk 11. The optical disk drive 10 has an optical pick-up unit (OPU) 12, a spindle motor 14, a motor controller 16, a focusing controller 18, a tracking controller 20, a microprocessor 22, a servo system 24, and a signal converter 26. The OPU 12 emits a laser Li with a predetermined wavelength and predetermined power to the optical disk 11. It is well-known that spiral track 28 is formed on the optical disk 11. In addition, the track 28 records a plurality of lands and pits with different lengths for storing eight-to-fourteen modulation (EFM) data. For example, the land corresponds to the low logic value “0”, and the pit corresponds to the high logic value “1”. In addition, when the laser Li spots the pits and lands on the track 28, the laser Li is modulated by the pits and lands to generate a reflecting laser Lr. The magnitude of the reflecting laser Lr generated from the laser Li spotting the land is greater than the magnitude of the reflecting laser Lr generated from the laser Li spotting the pit. Therefore, the OPU 12 is capable of detecting the reflecting laser Lr to generate a corresponding analog electric signal EFMa. Then, the signal converter 26 transforms the analog electric signal EFMa into a digital electric signal EFMd. In the end, the microprocessor 22 decodes the received digital electric signal EFMd to obtain wanted data DATA stored on the optical disk 11.
In addition, when the optical disk 11 is loaded into the optical disk drive 10, the microprocessor 22 drives the motor controller 16 to adjust rotation speed associated with a spindle of the spindle motor 14, and the microprocessor 22 also drives the servo system 24 to control the position of the OPU 12 corresponding to the optical disk 11. As mentioned above, the OPU 12 adopts the optical means to retrieve the data recorded by the track 28. Therefore, if the laser Li cannot be precisely focused on the track 28, the electric signal EFMa generated from the OPU 12 contains erroneous information. Similarly, if the laser Li forms a spot on the optical disk 11, and the location of the spot is deviated from the target track 28, the electric signal EFMa generated from the OPU 12 contains incorrect information. Therefore, when the OPU 12 is operating, the OPU 12 generates a focusing error signal FEO and a tracking error signal TEO. Then, the focusing controller 18 calculates a focusing driving signal FOO to the servo system 24 according to the focusing error signal FEO, and the tracking controller 20 calculates a tracking driving signal TRO to the servo system 24 according to the tracking error signal TEO. Thus, the servo system 24 is capable of moving the OPU 12 vertically for adjusting a vertical gap between the OPU 12 and the optical disk 11 through the focusing driving signal FOO, and is capable of moving the OPU 12 horizontally for adjusting a horizontal displacement of the OPU 12 above the optical disk 11 through the tracking driving signal TRO.
From the above description, it is understood that the focusing operation and the tracking operation for the OPU 12 greatly affect accuracy of the final electric signal EFMa. If the signal quality of the electric signal EFMa is bad, the wanted data DATA cannot be correctly obtained even if the microprocessor 22 enables an error correction mechanism. Therefore, the OPU 12 has to accurately generate the focusing error signal FEO and the tracking error signal TEO. Otherwise, the focusing controller 18 and the tracking controller 20 are unable to figure out the wanted tracking driving signal TRO and the focus driving signal FOO. In other words, the servo system 24 cannot move the OPU 12 to a correct position for retrieving data recorded on the track 28 of the optical disk 11.
Before the optical disk drives 10 leave the factory, component characteristic of the OPU 12 need to be carefully tested to filter out optical disk drives 10 having abnormal OPUs 12. Please refer to FIG. 2, which is a diagram of a prior art optical disk drive diagnosing system 40. The diagnosing system 40 includes the optical disk drive 10 shown in FIG. 1, a dynamic signal analyzer 42 (HP35670A for example), and a mixer 44. The optical disk drive 10 shown in FIG. 2 only contains the OPU 12, the focusing controller 18, the tracking controller 20, and the servo system 24 for simplicity. Input ports A, B of the dynamic signal analyzer 42 are respectively connected to the OPU 12 and the focusing controller 18. That is, the tracking error signal TEO outputted from the OPU 12 is passed to the input port A of the dynamic signal analyzer, and the focusing driving signal FOO calculated by the focusing controller 18 is delivered to the input port B of the dynamic signal analyzer 42. In addition, an output port C of the dynamic signal analyzer 42 outputs a testing signal TEST to the mixer 44. The testing signal TEST functions as a noise to interfere with the focusing driving signal FOO calculated by the focusing controller 18. As shown in FIG. 2, the mixer 44 finally mixes the focusing driving signal FOO and the testing signal TEST, and outputs a test focusing driving signal FOO″ to the servo system 24. The testing signal TEST generated from the dynamic signal analyzer 42 is used for simulating a noise, and is generally a sine wave with a frequency gradually increased from an initial value toward a target value. At the same time, the test focusing driving signal FOO″ influenced by the testing signal TEST is inputted into the servo system 24. Then, the servo system 24 adjusts a vertical gap between the OPU 12 and the target track 28 of the optical disk 11 according to the test focusing driving signal FOO″. With an appropriate adjustment, the laser emitted from the OPU 12 is capable of focusing on the track 28 of the optical disk 11. When the frequency of the testing signal TEST varies from the initial value toward the target value for affecting the focusing driving signal FOO, a user can use the tracking error signal TEO and the focusing driving signal FOO respectively received at input ports A, B of the dynamic signal analyzer 42 for analyzing a frequency response associated with the focusing driving signal FOO and the tracking error signal TEO.
Please refer to FIG. 3 in conjunction with FIG. 4. FIG. 3 is a first frequency response diagram associated with the focusing driving signal FOO and the tracking error signal TEO, and FIG. 4 is a second frequency response diagram associated with the focusing driving signal FOO and the tracking error signal TEO. In FIG. 3 and FIG. 4, the horizontal axis stands for the frequency, and the vertical axis stands for the gain. The response curve L2 shown in FIG. 4 corresponds to a standard OPU 12, and the response curve L1 shown in FIG. 3 corresponds to a flawed OPU 12. It is obvious that when the frequency of the testing signal TEST is greater than 10 KHz, the gains corresponding to the response curve L1 are greatly deviated from the gains corresponding to the response curve L2. Taking the frequency F for example, the gain, which corresponds to the frequency F, is equal to 25 through the response curve L1. However, the gain, which corresponds to the frequency F, is equal to 45 through the response curve L2. In other words, the crosstalk inherent to the flawed OPU 12 seriously affects the tracking error signal TEO and the focusing error signal FEO. Therefore, the tracking error signal TEO generated from the OPU 12 is introduced to the focusing error signal FEO generated from the OPU 12, and the unwanted interference couples with the focusing error signal FEO. Similarly, the focusing error signal FEO generated from the OPU 12 is introduced to the tracking error signal TEO generated from the OPU 12, and the unwanted interference couples with the tracking error signal TEO. The OPU 12 with serious crosstalk effect can be filtered out through observing the frequency response associated with the focusing driving signal FOO and the tracking error signal TEO or observing the frequency response associated with the tracking driving signal TRO and the focusing error signal FEO.
In order to diagnose characteristics of the OPU 12, a tester needs an external dynamic signal analyzer 42 and an external mixer 44 shown in FIG. 2. In addition, the dynamic signal analyzer 42 needs to be connected to the OPU 12 and the focusing controller 18, and the mixer 44 needs to be connected to the dynamic signal analyzer 42, the focusing controller 18, and the servo system 24. Concerning the optical disk drivers 10 waiting to be tested, the complicated connection shown in FIG. 2 is repeatedly established for diagnosing the characteristic of the OPU 12 within each optical disk driver 10. When mass production of the optical disk drive 10 begins, the prior art quality assurance (QA) procedure greatly slows actual yield of the optical disk drive 10 owing to the above-mentioned complicated testing mechanism.